IL21 and psoriasis: In a recent meta-analysis of 2876 psoriasis patients, increased serum levels of TNF-α, IFN-γ, IL-2, IL-6, IL-8, IL-18, and IL-22 in comparison with 2237 healthy controls have been documented, whereas no differences were found in the levels of IL-1β, IL-4, IL-10, IL-12, IL-17, IL-21, and IL-23 [31].